1. Field of the Invention
The present invention relates generally to magnetic disk drives with load/unload structure and, more particularly, to a load/unload structure having a lubricant reservoir.
2. Description of the Background Art
A magnetic disk drive storage device typically comprises one or more thin film magnetic disks, each having at least one data recording surface including a plurality of concentric tracks of magnetically stored data, a spindle motor and spindle motor controller for supporting and rotating the disk(s) at a selected RPM, at least one read/write transducer or xe2x80x9cheadxe2x80x9d per recording surface formed on a slider for reading information from and writing information to the recording surface, a data channel for processing the data read/written, a positionable actuator assembly for supporting the transducer in close proximity to a desired data track, and a servo system for controlling movement of the actuator assembly to position the transducer(s) over the desired track(s).
Each slider is attached on one surface to an actuator arm via a flexible suspension and includes on an opposite side an air bearing surface (ABS) of a desired configuration to provide favorable fly height characteristics. As the disk rotates, an air flow enters the slider""s leading edge and flows in the direction of its trailing edge. The air flow generates a positive pressure on the ABS, lifting the slider above the recording surface. The slider is maintained at a nominal fly height over the recording surface by a cushion of air.
To avoid the problems associated with contact start/stop recording, some disk drive designs employ xe2x80x9cload/unloadxe2x80x9d technology. According to this design, a ramp is provided for each slider/suspension assembly at the inner or outer diameter of the disk where the slider is xe2x80x9cparkedxe2x80x9d securely while the spindle motor is powered down. During normal operation, the disk speed is allowed to reach a selected RPM (which may be below the normal operating RPM) before the head is xe2x80x9cloadedxe2x80x9d onto the disk from the ramp on the air cushion generated by the disk""s rotation. In this manner, the slider flies over the disk without significant contact with the disk surface, eliminating contact start/stop wear. The load/unload ramp structure is generally made of plastic which can be injection molded into complex ramp structures.
With lower fly heights between the transducer head and the magnetic disk during operation of the disk drive, there is an increasing rate of intermittent contacts between the head and the disk resulting in damage to the disk surface. Although the disk is coated with lubricant during manufacture to protect it from such intermittent contact, during operation of the drive, the lubricant is depleted from the surface of the disk. Because of the problems associated with lubricant spin-off from the disk, a vapor phase lubricant reservoir system has been disclosed as a means for continuously maintaining a uniform lubricant film on the disk as described in U.S. Pat. No. 4,789,913 issued Dec. 6, 1988. The patent describes a method for lubricating the disk during operation of the drive. This method of lubrication continuously maintains the lubricant film on the disk drive during operation of the drive. Although this lubricant reservoir system will continuously lubricate the disk while the disk drive is operational, under the condition of prolonged shutdown a negligible amount of circulated airflow will occur and disk surface will not be sufficiently lubricated. Coupled with this inactivity is the possibility that the stored disk drive may experience a significant temperature gradient thereby causing a slow reduction in the thickness of the lubricant film on the disks. Although this stressed condition is readily corrected during operation of the disk drive, wear can occur during startup of the disk drive, especially during the critical phase of loading the heads onto the surfaces of the disks. During the initial loading, the heads in the head stack can come into intermittent contact with the disk until a lubricating thin-film bearing is established. Without adequate lubrication, the contact forces (between head and disk) may eventually cause debris evolution and pickup which eventually leads to head/disk failure. Therefore, there is a need in the art for a method of lubricating the head disk interface during shutdown of the disk drive.
It is the object of the present invention to provide a load/unload structure having lubricant reservoirs for lubricating the head surfaces during shutdown of the disk drive. Other objects and advantages will be apparent from the following disclosure.
The present invention relates to a magnetic disk drive for reading or writing magnetically, comprising: (i) a base plate; (ii)one or more of magnetic disks; (iii) a hub fixedly attached to the disks for supporting the disks; (iv) a motor attached to the base plate and operable to rotate the hub; (v) one or more magnetic read/write heads, each associated with the surface of a disk; (vi) one or more actuators for supporting the head(s) and moving the head(s) across the disk(s); and (vii) a load/unload structure comprising an elongated body, a base portion fixedly attached to the base plate and one or more ramps extending outwardly from the body. In one embodiment, each ramp is provided with a porous lubricant reservoir preferably positioned near the heads parked on the ramp. Lubricant having a high vapor pressure is disposed in the reservoir. During shutdown of the drive when the heads are parked on the ramps, the lubricant from the reservoirs will maintain a thin adsorbate film of lubricant on the head(s). The present invention minimizes the vapor-phase concentration gradient between reservoir unit and nearest head so as to maintain a well-controlled lubricant film on the surface of the head. In an alternative embodiment, the lubricant reservoir(s) are positioned on the body of the load/unload structure near the heads parked on the ramp.
A more thorough disclosure of the present invention is presented in the detailed description of the invention, which follows, and the accompanying figures.